tracing: Add "uptime" trace clock that uses jiffies

Add a simple trace clock called "uptime" for those that are
interested in the uptime of the trace. It uses jiffies as that's
the safest method, as other uptime clocks grab seq locks, which could
cause a deadlock if taken from an event or function tracer.

Requested-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/include/linux/trace_clock.h b/include/linux/trace_clock.h
index d563f37e1a1dfcfb3588c05b2117737448b3da18..1d7ca2739272b750be29f8ba2c898ab8950cd542 100644 (file)
--- a/include/linux/trace_clock.h
+++ b/include/linux/trace_clock.h
@@ -16,6 +16,7 @@
 
 extern u64 notrace trace_clock_local(void);
 extern u64 notrace trace_clock(void);
+extern u64 notrace trace_clock_jiffies(void);
 extern u64 notrace trace_clock_global(void);
 extern u64 notrace trace_clock_counter(void);
 

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index f90ca16afcf2401b90ec85f24fffa631b576632f..8eabfbb8003e33d0b06a5e5e331feeddcf90fe40 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -647,6 +647,7 @@ static struct {
        { trace_clock_local,    "local",        1 },
        { trace_clock_global,   "global",       1 },
        { trace_clock_counter,  "counter",      0 },
+       { trace_clock_jiffies,  "uptime",       1 },
        ARCH_TRACE_CLOCKS
 };
 

diff --git a/kernel/trace/trace_clock.c b/kernel/trace/trace_clock.c
index aa8f5f48dae610566f4b777119e1b3735b43170f..26dc348332b798eeb43a77cf2d89357512d9e8c0 100644 (file)
--- a/kernel/trace/trace_clock.c
+++ b/kernel/trace/trace_clock.c
@@ -57,6 +57,16 @@ u64 notrace trace_clock(void)
        return local_clock();
 }
 
+/*
+ * trace_jiffy_clock(): Simply use jiffies as a clock counter.
+ */
+u64 notrace trace_clock_jiffies(void)
+{
+       u64 jiffy = jiffies - INITIAL_JIFFIES;
+
+       /* Return nsecs */
+       return (u64)jiffies_to_usecs(jiffy) * 1000ULL;
+}
 
 /*
  * trace_clock_global(): special globally coherent trace clock